2,9-Dicarboxyquinacridone and methods for its production

ABSTRACT

This invention relates to 2,9-dicarboxyquinacridone and to methods for its preparation.

United States Patent Ehrich et a1.

[451 Mar. 25, 1975 2,9-DICARBOXYQUINACRIDONE AND METHODS FOR ITS PRODUCTION Inventors: Felix Frederick Ehrieh, Mexico City, Mexico; Edward E. Jaffe, Union, NJ.

E. I. du Pont de Nemours and Company, Wilmington, Del.

Filed: Mar. 7, 1973 Appl. No.: 338,687

Related US. Application Data Division of Scr. No. 140,984, May 6, 1971, Pat. No. 3,752,817.

Assignee:

US. Cl 260/279 R Int. Cl C07d 39/00 Field of Search 260/279 R References Cited UNITED STATES PATENTS 11/1961 Struve 260/279 R Primary ExaminerDonald G. Daus This invention relates to 2,9-dicarboi yquinzieridone I ABSTRACT and to methods for its preparation.

2 Claims, N0 Drawings 1 fl- XQUMQM QN AND. M T O i '7 I FOR ITS PRODUCTION BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION In accordance with the invention there is provided 2,9-dicarboxyquinacridone, a novel red-colored quinacridone derivative which is characterized by a high level of color stability in plastic extrusions at temperatures up to about 320C.

2,9-Dicarboxyquinacridone has the following formula and in a preferred embodiment of the invention is prepared by the steps of l) reacting succinyl succinic acid ester with alkyl p-aminobenzoate, (2) cyclizing the product dialkyl 2,5-di-(4-carbalkoxyanilino)-3,6- dihydroterephthalate of formula node to give a 2,9-dicarbalkoxy-6,l3-dihydroquinacridone of formula and (3) hydrolyzing and oxidizing the compound II. In

this invention are characterized by cleanness, bright- ALTERNATIVE PROCESS EMBODIMENTS Examples 1, 2 and 3 illustrate three alternative routes for preparing 2,9-dicarboxyquinacridone. Parts and percentages in the examples are by weight unless otherwise indicated.

EXAMPLE 1 This synthesis is carried out as follows: one mole of an ester of dialkylsuccinylsuccinateis reacted with two moles of alkyl p-aminobenzoate using the eutectic mixture of biphenyl and diphenyl oxide (Dowtherm A) as a solvent and p-toluenesulfonic acid as a catalyst to produce dialkyl 2,5-di-(4-carbalkoxyanilino)-3,6- dihydroterephthalate I. This intermediate product is heated in boiling Dowtherm. to effect cyclization to 2,9- dicarbalkoxy-6,l3-dihydroquinacridone II. By oxidation and hydrolysis of the 2,9-dicarbalkoxy-6,l3- dihydroquinacridone,-the desired product, 2,9-dicarboxyquinacridone is obtained.

A. Preparation of dialkyl 2,5-di-(4-carbethoxyanilino)- 3,6-dihydroterephthalate (where alkyl is methyl/ethyl) To a one-liter flask equipped with an agitator and means for introducing nitrogen to maintain an inert atmosphere within the flask, are added the following:

34.8 grams (0.144 mole) of a mixture of the methyl and ethyl esters of succinyl succinic acid 52.4 grams (0.318 mole) of ethyl p-aminobenzoate 0.5 gram (0.0026 mole) of p-toluenesulfonic acid monohydrate 78 ml. Dowtherm v The reaction mixture is subjected to a vacuum of about 15 mm. and is heated for six hours at 100C. At the conclusion of the heating period, the flask contents are brought to atmospheric pressure by allowing nitrogen to blanket the mixture, and cooled to 65C.

To the flask and contents are then added 150 cc. I

methanol and the mixture stirred for 30 minutes, cooled to 25C. and the precipitate filtered, washed with three portions of methanol of 150 cc. each, and air dried. The yield of product, based on the weights of reactant used is 94.6%. B. Preparation of 2,9-dicarbalkoxy-6,13- dihydroquinacridone (II where R is methyl/ethyl) Fifty and six-tenths grams of the mixture of dimethyl and diethyl dihydroterephthalates as produced in A is reslurried in 202 cc. Dowtherm and heated to C. to effect complete solution. The solution is transferred to an addition funnel, and held at l35-145C. under nitrogen. This solution is added over a period of 90 minutes to 202 cc. of well-agitated refluxing Dowtherm, also under a nitrogen atmosphere. After the addition is complete, the

pyrolysis mixture is stirred for 30 minutes at reflux, cooled to 40C., filtered, washed free of Dowtherm with methanol, and dried. The yield of II is 95.4% based on the ester terephthalate I used. Analysis gave the following results:

2,5-di-(4-carbethoxyanilino)-3 ,6-.

Calculated for C M teo. Found c 68.l2% 68.2% H 4.93% 4.8% N 5.47% 6.12%

C. Preparation of 2,9-dicarboxyquinacridone in First Polymorphic Form Two hundred fifty two grams of a press cake comprising 1 10.5 grams of 11 prepared as in B and 141.5 grams of methanol is stirred into 228 grams of methanol, and 236 grams of water is added. While keepingthe temperature of the mixture below 40C., a solution of 101.4 grams of potassium hydroxide in 124 grams of water is added. The'mixture is stirred for one and onequarter hours while maintaining the temperature at 25 to 40C., thus forming the potassium salt of 11. At the conclusion of this heating period, a solution of 54 grams of sodium m-nitrobenzene sulfonate in 72 grams of water is added with stirring. This solution is rinsed into the reaction mixture using 72 grams additional water. The mixture is heated and maintained at reflux for four hours to effect hydrolysis and oxidation of 11. Then heating is discontinued and 200 grams of water is added bringing the temperature to 6065C. Stirring is continued for minutes and 148 grams of sodium chloride is added. By ion-exchange the potassium salt of 11 becomes the sodium salt which precipitates due to excess sodium chloride. After an additional 15 minutes of stirring (still at 6065C.) the slurry is filtered, the precipitate washed with portions of 2% (volume basis) acetic acid until chloride-free thus forming the 2,9-dicarboxyquinacridone 111. The yield is found to be 97% based on the weight of 2,9-dicarbalkoxy-6,l3- dihydroquinacridone used.

The product exhibits an X-ray diffraction pattern characterized by one strong, one medium and five weak bands of the following interplanar spacings in Angstrom units: 16.05 (weak), 6.55 (medium), 6.10 (strong), 5.06 (weak), 4.11 (weak), 3.45 (weak), and 3.23 (weak).

D. Preparation of 2,9-Dicarboxyquinacridone in Second Polymorphic Form 1 The oxidation andhydrolysis of 11 is repeated through the step of refluxing the reaction mixture for 4 hours. The reaction mixture now containing the potassium salt of ll and excess KOH, is cooled to 60-65C. and acetic acid added to effect neutralization of the excess hydroxide and acidification of the mixture to a pH of 4.6-4.8. The mixture is stirred for 15 minutes while maintaining the temperature at 60-65C., and the slurry filtered, the pigment washed until acid free, and dried. The second polymorphic form of 2,9 -dicarboxyquinacridone thus obtained is characterized by an X-ray diffraction pattern of two strong, one medium, and four weak bands of the following interplanar spacings in Angstrom units: 17.66 (weak), 6.06 (strong), 5.75 (medium), 5.06 (weak), 4.23 (weak), 3.65 (weak), and 3.23 (strong).

This same polymorphic modification is alternatively obtained by dissolving 30 grams of 98% H SO at 85C. and drowning rapidly into an excess of water. The resulting slurry is boiled for three hours, filtered, washed acidand sulfate-free and dried.

In this example it will be noted that part A involves a reaction carried out for six hours at a temperature of 95 to 100C. in a Dowtherm medium, the product thereafter being washed with several portions of methanol. The purpose of this washing is to remove any excess p-aminobenzoate present with the precipitate. Although as described the methanol-wet cake in A was dried before further processing, it has been found that such drying step can be omitted and the methanolwet press cake diluted with Dowtherm and the resulting slurry heated to 145C. while distilling off methanol.

The solution of the ester, still containing some alcohol, is slowly added to boiling Dowtherm in order to effect the cyclization reaction. The presence of some methanol in the solution has no detrimental effect on the quality or yield of 11.

EXAMPLE 2 This alternative method for the preparation of 111 is shown in the following series of reactions:

dialkyl succinylsuccinate is reacted with paminobenzoic acid under acid catalysis to yield dialkyl- 2,5-(4-carboxyanilino)-3,6-dihydroterephthalate:

use.

H H r H 0 R0 0 H 0 C003 H .H

HOOC

where R is methyl or ethyl The compound IV is hydrolyzed and oxidized to yield H 3000 1100a N N calculated for CZflHZQNQOR:

% N found:

The melting point of the product is found to be 347350C.

B. Preparation of 2,5-di(carboxyanilino)-terephthalic acid (V) Fifty grams of the product of A is mixed with 500 grams ethanol, 50 grams sodium salt of m-nitrobenzene sulfonic acid, 30 grams of NaOH dissolved in 250 ml. H 0 and then the mixture is heated under reflux for 4.5 hours. The mixture is cooled by addition of 2.5 liters COOH COOH For a composition of C I-N 0 Calculated Found C 60.5 59.74 H 3.17 3.94 N 6.42 6.90

C. Cyclization of V to 2,9-dicarboxyquinacridone (III) To effect cyclization of V, 22.3 grams of V obtained as shown in B is introduced into 300 grams polyphosphoric acid and the mixture stirred and heated to l40l50C. The tetracarboxylic acid dissolves in the polyphosphoric acid on heating of the mixture, but as the cyclization progresses, a red product comes out of solution. The mixture is held at 140-150C. for three hours and then cooled. While keeping the temperature at about 50C., 300 ml of water is added slowly to effect hydrolysis of the conjugate acid of the cyclized product. The product, a different shade of red than the conjugate acid, is filtered and washed acid free. The weight of the product III is 20.6 grams representing a 100% yield. Its X-ray pattern is identical to that of Example l-C. D. Purification of 2,9-dicarboxyquinacridone (Ill) The crude product 1" prepared according to the process of C is purified by recrystallization as follows:

Forty grams of the crude product of C is dissolved at l0C. in 600 grams of 100% H SO When solution is complete (as indicated by microscopic examination of the solution), the acid concentration is lowered to 90% by careful addition of a calculated amount of water, maintaining the temperature at about C. The

precipitated sulfate is filtered on a sintered funnel, washed with about 85% H SO, and decomposed with ice. The liberated 2,9-dicarboxyquinacridone is filtered and washed with water until free of acid. The yield is 32.3 grams. Its X-ray pattern is identical to that of Example l-D.

For further purification, five grams of the recrystallized product is refluxed for 3 hours in 500 ml dimeth- 2 liters methanol 82 grams (0.6 mole) p-aminobenzoic acid 3 ml. concentrated HCl At the conclusion of the heating time the flask is cooled and the contents filtered, washed with water until free of chloride and dried. The yield is 88.0 grams of the mixed ester of IV (thus 90.7%). Steps B and C may then be followed leading to the preparation of III.

EXAMPLE 3 In still anoather alternative method for preparation of III, the intermediate dialkyl 2,5-di-4-carboxyanilino- 3,6-dihydroterephthalate IV, the preparation of which has been shown in Example 2, is cyclized in a high boiling solvent to 2,9-dicarboxy-6,13-dihydroquinacridone of formula VI:

Hooc Rooc N COOR The desired compound 2,9-dicarboxyq'uinacridone III is obtained from VI by oxidation with sodium mnitrobenzene sulfonate in alcoholic sodium hydroxide. A. Preparation of 2,9-dicarboxy-6, l 3- dihydroquinacridone (VI) Nine and one-half grams of diethyl-2,5-(4- carboxyanilino)-3,6-dihydroterephthalate is suspended in 250 ml. of Dowtherm and heated to l160C. while maintained under a nitrogen atmosphere. The thin slurry is added to 250 ml. of boiling Dowtherm over a period of 45 minutes. Reflux is continued for another two hours and the resulting slurry is cooled to 120C., the solid isolated by filtration, and washed with methanol. The yield is 7.8 grams and the analysis is as follows: I

yl-formamide, filtered, and washed with methanol. 50 Four and one-half grams of purified product III is ob- Calculated CzzHuNzosi Found tained. Analysis ShOWSI C 65 C 42% H 3.48% H 3.9% Calculated for CMHHNZOG Found N 6.96% N 6.4%

B. Preparation of 2,9-dicarboxyquinacridone (III) from 2,9-dicarboxy-6, l 3-dihydroquinacridone V] For this preparation, 7.7 grams of VI prepared as in part A is added to a solution of 48 grams of methanol,

45 grams of water and 12 grams sodium hydroxide.

After stirring this suspension for 1 /2 hours, a solution of 4 /2 grams sodium salt of m-nitrobenzene suflonic acid in 18 grams of water is added. The reaction is'carried out under reflux for 2 hours, is diluted with water until a total volume of 2 liters is obtained, and 50 grams of glacial acetic acid is then added. Thereafter the mixture is stirred for 10 minutes, filtered, washed acidfree, and dried. The yield is 6.6 grams of product. This material is acid recrystallized according to process of Example 2-D to yield 3.8 grams of a material which is identified as III.

In a modification of part A of Example 1, the reaction can be carried out in solvents other than Dowtherm such as methyl, or ethyl alcohol and under these conditions no vacuum is required.

Although in Example l-A, ethyl p-aminobenzoate is used as the amine for the reaction, other alkyl paminobenzoates can be used wherein the alkyl is of l-4 carbons, for example methyl p-aminobenzoate, propyl p-aminobenzoate, etc.

In Example 1 the preparation of I and Example 2 the preparation of IV is catalyzed by an acid. In Example 1 it is p-toluenesulfonic acid and in Example 2 it is hydrochloric acid. Other catalysts, such as trifluoroacetic acid in an anhydrous form, can be used with equal success.

PARTICLE SIZE REDUCTION Examples 4 and 5 illustrate alternative methods for reducing the particle size of 2,9-dicarboxyquinacridone to suitable pigmentary dimensions.

EXAMPLE 4 This example illustrates particle size reduction of 2,9-dicarboxyquinacridone by salt milling.

Fifteen and six tenths grams of the product III obtained according to Example I is placed in a ball mill with 135.0 grams of Al (SO.,) .l8I-I O and 2.4 grams of tetrachloroethylene and sufficient steel shot and roofing nails to half-fill the mill. The mill is rotated in the conventional manner at about 75% of critical speed for approximately 70 hours. The shot and nails are then separated from the pigment powder by screening and the powder product is added to 2,000 parts of water mixed with 80 parts H SO The resulting slurry is heated to about 90C., stirred for approximately one hour, filtered, washed, and dried in the conventional manner. The pigment is then pulverized.

EXAMPLE 5 This example illustrates particle-size reduction of 2,9-dicarboxyquinacridone by acetone milling.

Twelve grams of the product III obtained according to Example I is placed in a glass jar with 79 grams of acetone and 600 grams of steel shot of 0.125 inch diameter. After rotating the mill in the conventional manner for approximately 72 hours, the mill is discharged and the pigment is rinsed from the shot over a strainer by adding additional acetone. The resulting slurry in 2,000 parts of water is heated to about 90C. to boil off the acetone, 36 parts of concentrated sulfuric acid is added, and the slurry is then boiled and stirred for 1.5 hours prior to filtering, and washing with water. The dried pigment is pulverized.

In Example 4 where the particle size reduction by salt milling the 2,9-dicarboxyquinacridone is shown, the salt is aluminum sulfate; however, other salts can be used with equal success. Salts such as sodium chloride,

potassism chloride, hydrated aluminum sulfate, sodium sulfate and ammonium carbonate may be used.

Although in Example 5 the milling cycle was hours, this milling time is not'intended as limiting. Other milling cycles can be used and, in fact, milling cycles of 20 and 30 hours have been used to give products of even better dispersibility; however, with some sacrifice in strength.

Other methods of particle size reduction that may be employed are those employing high temperature acid drowning techniques or acid swelling techniques. Utility of 2,9-dicarboxyquinacridone in Plastic Compositions Pigmentary 2,9-dicarboxyquinacridone is an especially useful colorant in plastics, particularly those which require fabrication techniques carried out at high temperatures. The general procedure for evaluation of pigments as colorants in plastics is first to mix the dried pigment (together with extenders such as titanium dioxide, if desired) and the solid granular resin, and subject this mixture to vigorous stirring until homogeneity has been achieved. This blending operation may be carried out in any one of a wide variety of devices such as a ribbon blender,- Banbury mixer, Baker- Perkins Mixer, or more simply by tumbling end-overend in a closed container. The plastic pigment mixture is then injection-molded into chips at a temperature above the softening temperature of the plastic. For polystyrene, acetal resins, acrylic resins, polyester resins, and polyamides such as Zytel nylon resins, extrusion temperatures of from about C. to about 320C. are used. Examples 6 through 9 show the use of 2,9-dicarboxyquinacridone as a colorant in several plastic resins.

EXAMPLE 6 A mixture is prepared consisting of 5982 grams of a commercial acetal molding resin, 18 grams ofpigmentary rutile titanium dioxide, and 0.30 gram of pigmentary 2,9-dicarboxyquinacridone. The mixture is first extruded at 185 to C. into strands. Then the strands are cut into granules and molded into step chips at 200C. The chips have a bright pink color which is superior in depth of color, cleanness'of hue, and heat stability as compared with similarly prepared chips employing linear quinacridone as the colorant. The latter pigment undergoes a marked color change, i.e. to a yellow hue, when processed at the high temperatures.

EXAMPLE 7 A. Using the same procedure as given above in Example 6, the mixture of the following materials is fabricated into step chips:

6800 grams polymethylmethacrylate resin 27.2 grams of rutile titanium dioxide 3.0 grams 2,9-dicarboxyquinacridone pigment Both the compounding extrusion and the molding of the chips is carried out at 250C. The chips are a bright, bluish-pink color of attractive depth of hue, cleanness, uniformity and heat stability. B. Transparent chips are prepared using the same amounts of resin and colorant as in A, but omitting the titanium dioxide component. In this case, two sets of step chips are molded: one set at 250C. and the other at 283C. Both sets of chips are a translucent red and no difference in color between the two sets of chips can be observed.

EXAMPLE 8 In this example, pigmentary 2,9-dicarboxyquinacridone is used as a colorant for nylon resin.

Four thousand grams of nylon molding flake is tumbled with 20.0 grams of rutile titanium dioxide and 0.3 gram of pigmentary 2,9-dicarboxyquinacridone. The resulting mixture is compounded through an extruder at a temperature (barrel and die) of 270C. The nylon strands from the extruder are cut into granules and molded into step chips at 270C. The chips are of a clean bright pink color, definitely superior to similarly prepared nylon chips using 2,9-dimethylquinacridone as colorant. The latter undergo a marked color change to a yellower hue and exhibit intense fluorescence under ultraviolet light.

EXAMPLE 9 This example shows the excellent properties obtainable with the use of 2,9-dicarboxyquinacridone as a colorant for polystyrene extrusions.

One thousand grams of polystyrene powder are mixed with 1.0 gram pigmentary rutile titanium dioxide and 0.1 gram of pigmentary 2,9-dicarboxyquinacridone. The mixture is tumbled end-over-end in a closed container to obtain a uniform blend. The resultant colored powder is then injection molded into five sets of chips at 200C, 230C, 260C, 290C.,-and 320C., respectively. The degree of degradation undergone by the pigment during the extruding operation is determined by comparing the colors of the chips processed at the above temperatures. The results are as follows:

Rating at Extrusion Temperature 200C. 230C. 260C. 290C. 320C.

Product 10 9 9 8 Ill as colorant Bluish pink The color changes at the four higher temperatures are to be compared with the color of the chip extruded at 200C, a rating of 10 indicating complete color stability at the temperature indicated, 8 indicating slight change, 6 considerable change, 2 very bad degradation of color, and 0 indicating complete failure of the colorant. Under ultraviolet light, the chips pigmented with linear quinacridone exhibit marked fluorescence in contrast to the absence of fluorescence in chips pigmented with the product of this invention. It is considered that increased fluorescence is indicative of increased pigment solubility in the resin, which of course is undesirable.

What is claimed is:

1. A process for the preparation of 2,9-dicarboxyquinacridone of the chemical formula HOOC R'OOC where R is alkyl of l4 carbons,

2. effecting the cyclization of IV in a high boiling solvent to yield 2,9-dicarboxy-(6,13- dihydroquinacridone) of chemical formula and 3. oxidizing VI in alcoholic NaOH in the presence of sodium m-nitrobenzene sulfonate to 2,9-dicarboxyquinacridone III. 2. 2,9-dicarboxy-6,l3-dihydroquinacridone of formula yield HOOC 

1. A PROCESS FOR THE PREPARATION OF 2,9DICARBOXYQUINACRIDONE OF THE CHEMICAL FORMULA
 1. REACTING ALKYL SUCCINYLSUCCINATE WITH P-AMINOBENZOIC ACID IN A SOLVENT AT AN ELEVATED TEMPERATURE UNDER AN INERT ATMOSPHERE TO YIELD DIALKYL 2,5-DI-(4CARBOXYANILINO)-3,6-DIHYDROTEREPHTHALATE OF CHEMICAL FORMULA
 2. EFFECTING THE CYCLIZATION OF IV IN A HIGH BOILING SOLVENT TO YIELD 2,9-DICARBOXY-(6,13-DIHYDROQUINACRIDONE) OF CHEMICAL FORMULA
 2. effecting the cyclization of IV in a high boiling solvent to yield 2,9-dicarboxy-(6,13-dihydroquinacridone) of chemical formula
 2. 2,9-dicarboxy-6,13-dihydroquinacridone of formula
 3. oxidizing VI in alcoholic NaOH in the presence of sodium m-nitrobenzene sulfonate to yield 2,9-dicarboxy-quinacridone III.
 3. OXIDIZING VI IN ALCOHOLIC NAOH IN THE PRESENCE OF SODIUM M-NITROBENZENE SULFONATE TO YIELD 2,9-DICARBOXYQUINACRIDONE III. 